In recent years, HDDs and like magnetic disc devices are made available in smaller sizes with greater capacities, and with this trend, it is required to provide magnetic heads which are adapted for high-density recording at a low relative velocity. Accordingly, sliders for use in magnetic heads of the floating type must be so constructed that the magnetic head can be levitated with stability even at a low relative velocity at which the air film has low rigidity.
FIG. 2 is a perspective view showing a conventional floating head slider utilizing negative pressure. This conventional slider is formed, on the surface thereof to be opposed to magnetic discs, with two side rails 11, 12 extending approximately in parallel to the direction of travel of the magnetic disc, and with a cross rail 20 positioned on the air inflow side (disc advancing side) of the slider, having a longitudinal axis generally orthogonal to the side rails 11, 12 and interconnecting the side rails 11, 12. The slider further has a tapered portion 30 at the air inflow side, and thin film head elements 41, 42 at the air outflow side. The surfaces of the side rails 11, 12 and the surface of the cross rail 20 form the same plane to serve as a surface for producing a positive pressure, i.e., a levitative force, when the slider moves relative to the magnetic disc. The region having three sides surrounded by the two rails 11, 12 and the cross rail 20 is in the form of a recessed face 50, which acts as a surface for producing a negative pressure, i.e., suction acting toward the magnetic disc, when the slider moves relative to the disc.
As shown in FIG. 3, this negative pressure F is produced by an air stream 3 flowing into a space between the slider 1 and the magnetic disc 2, when the stream as compressed between the cross rail 20 and the disc 2 thereafter expands between the recessed face 50 and the disc 2 to form an expanded flow. The negative pressure acts in balance with the positive pressure afforded by the rigidity of air to the rails 11, 12, giving a stabilized amount of levitation to the slider even at a low relative velocity.
With the conventional floating head slider, however, the cross rail 20 is present at the air inflow side to prevent the air stream from escaping, so that the slider has the problem that the dust present on the magnetic disc or in the air ingresses into the space between the slider and the disc, causing damage to the slider or the disc or impeding stable levitation. Further since the air stream from the front of the slider is prevented from escaping, the slider front side is liable to be influenced by the pressure of air. This entails the problem of producing variations in the pitch angle, i.e., the angle of inclination of the slider with respect to the disc surface in the longitudinal direction of the slider.
For example, Examined Japanese Patent Publication HEI 2-230575 discloses a floating head slider which has overcome the above problems. This slider has a cross rail disposed approximately at the central portion only so as to be separate from two side rails.
The disclosed slider nevertheless has another problem. To be fully effective, the cross rail needs to have a small length, which then prevents occurrence of negative pressure, rendering the slider no longer floatable at a low position.
The slider has another problem in that a lateral blast of air acts on the slider owing to an inclination thereof with respect to the direction of its movement relative to the magnetic disc, rendering unstable the angle of inclination in the lateral direction with respect to the disc surface, namely, the roll angle. Moreover, the angle of inclination of the slider with respect to the direction of its movement relative to the disc, i.e., the skew angle, differs depending on whether the slider is positioned at the inner periphery of the magnetic disc or at the outer periphery thereof to alter the magnitude of the lateral stream of air, hence the problem that the levitated state of the slider at the disc inner periphery differs from that of the slider at the disc outer periphery.